Multi-dose cleaning products are commonly used in dishwashing and clothes washing applications. Multi-dose cleaning products typically include two or more different cleaning compositions in separate compartments (e.g., a detergent in one compartment and a rinse aid in another compartment). The amount of cleaning composition in each compartment is pre-measured so that the consumer does not have to measure an appropriate amount of each cleaning composition. Also, since each dose is packaged individually, the risk of skin contact with potentially irritating cleaning compositions is reduced. Additionally, multi-dose cleaning products allow a consumer to purchase a single product rather having to buy the cleaning compositions separately.
A multi-dose cleaning product typically comprises two or more water-soluble pouches, each filled with a respective cleaning composition (e.g., a powdered detergent, a liquid rinse aid, water softener, etc.). The exterior walls of the water-soluble pouches are typically very thin and thus susceptible to damage, particularly while the product moves through a supply chain. If the water-soluble pouches are exposed to water, water vapor, or any other potentially corrosive elements during their storage or transport, or at any other point prior to their use in a cleaning application, a risk exists that the water-soluble pouches will prematurely dissolve and release their contents. Furthermore, shifting and contact with other items during transport may inadvertently puncture the thin skin of the water-soluble pouches.
To protect the water-soluble pouches from damage, the pouches are typically placed inside a protective stand-up bag. These bags typically are made of a polyethylene (PE) film that is laminated with another material, such as polyethylene terephthalate (PET), to provide stiffness. While this kind of secondary packaging shields the water-soluble pouches from external elements, it has several downsides. If one of the water-soluble pouches breaks inside the bag due to, for example, mechanical shock, the damaged pouch may leak its contents and compromise the other water-soluble pouches in the bag. Also, it is typically necessary to include a re-sealing mechanism so that the consumer can re-seal the bag after removing the desired number of water-soluble pouches. Such a re-sealing mechanism increases the manufacturing costs of the bag. Additionally, the bags tend to be bulky and difficult to stack, and therefore oftentimes require a substantial amount of shelf space.
Another issue with water-soluble pouches is that their water-soluble film has the propensity to undergo “shrink-back” during thermoforming. This characteristic can prevent the full volume of the pouch from being utilized at the filing stage. To reduce the effects shrink-back, it is known to thermoform the water-soluble film together with a plastic carrier sheet, as described in U.S. Patent Publication No. 2004/0142131. An effect of thermoforming the water-soluble film and the plastic carrier sheet at the same time is that the water-soluble film acquires a temporary, or permanent, affinity for the plastic carrier sheet. As a result, the water-soluble film retains its shape and is less likely to experience shrink-back prior to filling. Accordingly, it is possible to utilize the full volume of the pouch at the filing stage. An additional benefit of the plastic carrier sheet is that it can serve as an external protective casing for the water-soluble pouches once the thermoforming process is complete. The plastic sheet thus eliminates the need to store the water-soluble pouches inside a protective external bag.
U.S. Patent Publication No. 2004/0142131 describes thermoforming a first water-soluble film to a first plastic carrier sheet, and subsequently, sealing a second water-soluble film and a second plastic carrier sheet over the top of the structure formed by the first water-soluble film and the first plastic sheet. The inclusion of the second plastic carrier sheet increases manufacturing costs and time. Also, the thermoforming process described in U.S. Patent Publication No. 2004/0142131 is only capable of producing unit dose cleaning products. This is because each external plastic compartment can only fit a single water-soluble pouch. Accordingly, the method described U.S. Patent Publication No. 2004/0142131 is not suitable for making multi-dose cleaning products.